ULTRA VIOLET-INDUCED CELLULAR INJURY AND POSSIBLE PARTICIPATION OF SULFUR-CONTAINING GLYCOLIPID IN ITS PREVENTION

本研究的目的是考察纤细裸藻作为植物模型和细小裸藻作为动物模型是否会在氧化胁迫下表现出不同的反应。如果可以发现任何差异，则研究了含硫糖脂-磺基喹诺酮二甘油酯(SQDG)的可能参与。首先，利用光子探针在荧光显微镜下测量细胞内脂质过氧化水平，比较了光照条件下和黑暗条件下培养的Z菌株和SMZ菌株在UV-B辐射下诱导的脂质过氧化程度。在光照条件下生长的Z菌株对UV-B诱导的细胞损伤具有最强的抗性。在脂质体体系中，SQDG本身具有清除自由基的作用，但对UV-B诱导的脂质过氧化反应有促进作用。在体内，抗氧化作用的发挥方式必须是复杂的。比较了在光照和/或黑暗条件下生长的Z菌株和SMZ菌株的8-OH-DG水平。在光照条件下生长的Z中其含量最低。有趣的是，裸藻的8-OH-DG水平远高于人类(比人类高出两个数量级以上)，反映了裸藻的衰老程度。这可能是由于裸藻的世代时间短至24小时所致。Euglena细胞似乎可能成为衰老研究及其预防的有用工具。综上所述，SQDG可能通过两种方式发挥抗氧化作用，即清除自由基诱导的过氧化作用和比其他生物膜脂更优先地被抗氧化酶如抗坏血酸过氧化物酶清除和降解。

A purpose of the present research was to examine whether Euglena gracilis Z as a plant model and E.gracilis SMZ as animal model might show different response under oxidative stress or not. And if any difference could be found, the possible participation of sulfur containing glycolipid, sulfoquinovosyldiglyceride (SQDG) was studied. Firstly, the extent of UV-B-induced lipid peroxidation on strains of Z and SMZ grown under illumination, and those grown in the dark were compared by measuring intracellular lipid peroxide level on fluorescence microscopy using photon probe. The Z strain grown under illumination was found most resistant against UV-B-induced cell damage. SQDG by itself was found in liposomal system to exhibit radical scavenger, however, it rather stimulated UV-B-induced lipid peroxidation. In vivo, the mode of antioxidative effect must be exerted in complicated. The levels of 8-OH-dG in Z and SMZ strains grown under light and/or dark was compared. Its level in Z grown under illumination was the lowest among examined. Interestingly, 8-OH-dG level of Euglena was far higher (more than two orders of magnitude higher of ten to the power) than that of human, the level of 8-OH-dG of Euglena reflects close link to the extent of aging. It may be due to short generation time of Euglena as short as 24 hours. It seems likely that Euglena cell would be a useful tool for aging research and its prevention. In conclusion, SQDG would exhibit antioxidative role in two ways ; i.e., radical scavenger against radical-induced peroxidation and peroxidized more preferentially than other biomembrane lipid so as to be eliminated and degraded by antioxidative enzymes such as Ascorbate Peroxidase.